The present invention contemplates drilling apparatus to be operable to rotate the drillstring, or at least the drillstring's drill head or bit, or both. The magnetic hammer is to be operable to provide vibration axially to the drill head or bit. To achieve this, the magnetic hammer or vibrational apparatus which acts as such a hammer, is positioned as part of the drillstring or in the drillstring.
In our patent specification WO2006/065155 (PCT/NZ2005/000329) we disclose a method of generating a shuttling effect reliant upon magnetic arrays being able to be rotated relative to each other by a mechanical drive to a confined shuttle. It had at least one magnetic array to rotate with the shuttle and at least one magnetic array of the complementary structures providing the confinement.
The embodiments disclosed in WO2006/065155 showed the generation of vibration by the shuttling of the shuttle being carried via a rotary mounting of a drillstring into the drillstring. The drillstring had a separate rotary drive below the shuttle and was rotatable independently of both the shuttle and the confinement structure.
The vibrational output from the spindled shuttle of WO2006/065155 was via the confinement structure and not from the shuttle itself and, in the case of a drillstring, had neither the confinement structure nor the spindled shuttle synchronised to the drillstring.
The present invention recognises an advantage to be derived for several types of drilling in having vibrational apparatus, as a magnetic hammer, positioned as part of the drillstring or in the drillstring and to have part thereof synchronised to the drillstring.
As used herein the term “as part of the drillstring” can mean at the top of the drillstring but rotating at least in part synchronously with the drillstring and below any rotational drive input to the drillstring it can also mean at the bottom of the drillstring as also can “in the drillstring”. The term “positioned . . . in the drillstring” means anywhere along the length of the drillstring below the rotational drive input to the drillstring if there is any.
Inclusion of the vibrational apparatus, with its magnetic arrays able to move relative to each other as part of or in the drillstring, provides other advantages.
One is the prospect of fluid drives being used multifunctionally.
Another advantage is an ability to hold part of the vibrational apparatus stationary with the drillstring even if a drive of some kind is still employed to rotate part of the vibrational apparatus anywhere along the length of the drillstring.
Another advantage arises from the ability for the hammering to be directed bidirectionally or unidirectionally, the latter if wanted to minimise damage in the opposite direction (eg, upwardly). This can be important when there is, above the vibrational apparatus in the drillstring, sensitive equipment or componentry.
Another advantage downhole is the ability to provide for the drillstring to carry at its lowest end a peripheral cutter to act in conjunction with an inner cutter, the inner part being clearly a bit or a drillhead and the peripheral part (preferably being synchronised to rotate with the drillstring) itself being a drillhead or bit.
It is a further or alternative object to provide drilling apparatus of a kind having a drillstring, operable to rotate the drillstring or at least the drillstring's drill head or bit, or both, and operable to provide vibration axially to the drill head or bit wherein vibrational apparatus, to provide the vibration, is positioned as part of the drillstring or in the drillstring.
It is a further or alternative object to employ a fluid drive to and/or from vibrational apparatus, or part thereof, of a drillstring.
It is yet a further or alternative object to provide for drillhead or bit rotation and/or vibration independently of drillstring rotation.
It is a further or alternative object to provide vibrational apparatus having a shuttling action of one or more assemblies thereof relative to the drillstring or each or one another yet deriving part of its drive via a transmission reliant on the state of rotation, if any, of the drillstring.
It is a further or alternative object to provide vibration to an inner cutter (drillhead or bit) and/or an outer cutter (drillhead or bit) of a drillstring.